Spectral-spatial imaging device

ABSTRACT

In general, an imaging system to synchronously record a spatial image and a spectral image of a portion of the spatial image is described. In some examples, a beam splitter of the imaging system splits an optical beam, obtained from a viewing device, into a first split beam directed by the imaging system to a spatial camera and a second split beam directed by the imaging system to the entrance slit of an imaging spectrograph that is coupled to a spectral camera. An electronic apparatus synchronously triggers the spatial camera and the spectral camera to synchronously record a spatial image and a spectral image, respectively.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/949,830, filed Nov. 16, 2020, which is a continuation of U.S. patentapplication Ser. No. 16/081,806, filed on Mar. 10, 2017, which is anational stage entry under 35 U.S.C. § 371 of PCT Application No.PCT/US2017/021787, filed Mar. 10, 2017, which claims the benefit of U.S.Provisional Application No. 62/306,520, filed Mar. 10, 2016. The entirecontents of U.S. patent application Ser. Nos. 16/949,830, 16/081,806,PCT Application No. PCT/US2017/021787, and U.S. Provisional ApplicationNo. 62/306,520 are incorporated herein by reference.

TECHNICAL FIELD

The disclosure relates to spectral imaging.

BACKGROUND

Optical spectra for light reflected from objects may be obtained byreplacing a conventional imaging system of a fore-optic device, such asa lens camera or microscope, with an imaging spectrograph. With thisconfiguration, optical spectra from a single line on the object areobtained by exposing the camera to light reflected from the object. Thelocations where spectra originate on the object are known onlyapproximately if a separate picture of the recorded surface is takenafterward. If the object is attached to a moving platform withcontrolled motion, or to a motorized microscope stage, a set of linescontaining spectra can be obtained, such that individual spectra can bereferenced to physical features of the object using hyperspectralimaging (HSI) methods. By this technique of motion-controlled movingplatform with HSI, a conventional image with the spectrum of every pointon a grid can be obtained, hence this method is commonly used to mapspectra to object features.

“Snapshot” HSI systems can obtain spectra from all points on an image ina single instant. However, such systems do not obtain a continuousspectrum with regularly spaced wavelengths, but rather one that has alimited number (less than thirty) of unequally spaced wavelengths, andwhich can require extensive computation to reconstruct.

SUMMARY

In general, an imaging system to synchronously record a spatial imageand a spectral image of a portion of the spatial image is described. Insome examples, a beam splitter of the imaging system splits an opticalbeam, obtained from a viewing device, into a first split beam directedby the imaging system to a spatial camera and a second split beamdirected by the imaging system to the entrance slit of an imagingspectrograph that is coupled to a spectral camera. An electronicapparatus synchronously triggers the spatial camera and the spectralcamera to synchronously record a spatial image and a spectral image,respectively.

The entrance slit of the imaging spectrograph defines an area of theimage to be separated into spectra by the imaging spectrograph. Becausethe first split beam and the second split beam are split from a commonoptical beam, the entrance slit of the imaging spectrograph defines thearea of the image that is separated into spectra and correlates to acorresponding area of the spatial image. The imaging system mayconsequently enable the synchronous spectral recording of the opticalspectra of points in a defined area of an image and recording of thespatial image for the image including the defined area. Because theoptical spectra of points in the defined area of the image map to thecorresponding points in the spatial image, the imaging system may enablethe assignment of optical spectra directly to physical featurescontained in a conventional image, by virtue of the one-to-one mappingbetween a spectra and a location in the images. In other words, theimaging system and techniques described here may allow users to producea substantially exact and documented assignment between recordings ofoptical spectra and the specific physical or structural features of themeasured object.

The image system may provide advantages in multiple fields that performanalysis based on chemometric spectral data, such as materials science,biomedical research, and medical diagnostics. In ophthalmology,applications may include retinal metabolic imaging, role of pigmentationin retinal disorders (macular degeneration, retinitis pigmentosa),blood-borne diseases, and Alzheimer's disease screening, as well asscreening for Parkinson's disease, Huntington's disease, and otheramyloid-related neurological diseases. In wound healing, applicationsmay include assessment for healing in chronic wounds and pathogendetection. As another example, if spectral recordings were to be used incolon cancer detection, the imaging system may permit the assignment ofthe spectral correlates of suspected cancerous tissue with specificstructural features of the tissue.

In one example, a spatial-spectral imaging apparatus includes a beamsplitter configured to receive a light beam carrying an image of anobject and to split the light beam into a first split light beam and asecond split light beam; an imaging spectrograph configured to receivethe first split light beam and disperse a range of wavelengths of thefirst split light beam to form a spectral image comprising a pluralityof spectra; a spatial image camera configured to receive the secondsplit light beam; and a spectral image camera configured to receive thespectral image from the imaging spectrograph, wherein the spectral imagecamera and the spatial image camera are configured to synchronouslyrecord, respectively, the spectral image and a spatial image carried bythe second split light beam.

In another example, an imaging system includes a retinal viewing deviceconfigured to output a light beam carrying an image of an object; and aspatial-spectral imaging apparatus comprising: a beam splitterconfigured to receive the light beam carrying the image of the objectand to split the light beam into a first split light beam and a secondsplit light beam; an imaging spectrograph configured to receive thefirst split light beam and disperse a range of wavelengths of the firstsplit light beam to form a spectral image comprising a plurality ofspectra; a spatial image camera configured to receive the second splitlight beam; and a spectral image camera configured to receive thespectral image from the imaging spectrograph, wherein the spectral imagecamera and the spatial image camera are configured to synchronouslyrecord, respectively, the spectral image and a spatial image carried bythe second split light beam.

In another example, a method includes triggering a spatial-spectralimaging apparatus having a spectral image camera and a spatial imagecamera to trigger the spectral image camera and the spatial image camerato synchronously record, respectively, a spectral image of an object anda spatial image of the object.

The details of one or more examples are set forth in the accompanyingdrawings and the description below. Other features, objects, andadvantages will be apparent from the description and drawings, and fromthe claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating an imaging system according totechniques described in this disclosure.

FIG. 2 is a recorded spatial image of a human fundus, according totechniques described herein.

FIG. 3 is a recorded spectral image which depicts the optical spectrumof each point along a line crossing the spatial image of FIG. 2,according to techniques of this disclosure.

FIG. 4 is a plot of the computed absorption spectrum of capillary bloodfrom the optic disc in the visible light spectrum, in accordance withtechniques of this disclosure.

FIG. 5 is a diagram illustrating a conceptual view of select parts of ahuman fundus.

FIG. 6 includes spatial images recorded by operation of an imagingsystem, according to techniques described herein.

FIGS. 7A-7D each depicts a correlated, recorded pair of spatial andspectral images of a part of a human fundus, recorded by operation of animaging system, according to techniques described in this disclosure.

FIGS. 8-9 include spatial images recorded by operation of an imagingsystem, according to techniques described herein.

FIGS. 10A-10D each depict a plot of average absorption spectra ofcapillary blood from a part of human fundi, in the visible lightspectrum, computed according to techniques described herein.

FIGS. 11A-11D each depict a plot of average absorption spectra ofcapillary blood from a part of human fundi, in the visible lightspectrum, computed according to techniques described herein.

Like reference characters denote like elements throughout the figuresand text.

DETAILED DESCRIPTION

FIG. 1 is a block diagram illustrating an imaging system according totechniques described in this disclosure. In this example, imaging system10 includes a spatial-spectral imaging apparatus 20 attached to aretinal viewing device 12. Retinal viewing device 12 may represent anophthalmic fundus camera or other device for obtaining images 50. Inthis example, images 50 are images of an ocular fundus 49 but images 50may be of any object. A light source (not show in FIG. 1) illuminatesthe fundus 49 to produce images 50 input to ophthalmological lens 14 ofretinal viewing device 12. While not illustrated in FIG. 1, the retinalviewing device 12 may include a reticulating arm having an attachedlight that allows the operator to control the gaze direction of the eyebeing viewed, for ophthalmalogical applications. Fundus 49 may be of ahuman or other living subject and have independent motion according tomuscular activity of the subject. In other words, the subject may havenormal eye motion resulting in movement of the fundus and correspondingdifferent images 50 over time.

Ophthalmological lens 14 includes one or more lenses configured tomodify images 50 to produce images 51. Retinal viewing device 12includes an eyepiece (or “ocular lens”) 16 to focus images 51 forviewing by a user (not shown) of retinal viewing device 12. Retinalviewing device 12 includes optical hardware configured to direct andoutput images 51 along an imaging path via output port 17. Output port17 may represent a secondary camera port of the retinal viewing device12.

According to techniques described in this disclosure, a spatial-spectralimaging apparatus 20 is attached to a retinal viewing device 12 toreceive the images 51 output via output port 17. Spatial-spectralimaging apparatus 20 includes an adaptor 18 configured to attach thespatial-spectral imaging apparatus 20 to retinal viewing device 12. Aoptical lens 30 focuses images 51 from retinal viewing device 12 to thespatial image camera 30 and the entrance slit of imaging spectrograph36.

Spatial-spectral imaging apparatus 20 includes an optical beam splitter35, positioned above the optical lens 30, to split the light beamtransporting images 51 into a transmitted light beam and a reflectedlight beam. Beam splitter 35 may represent a partially-reflectingmirror, a beam splitter cube, a pellicle, a membrane, or other devicefor splitting the light beam transporting images 51. The transmittedsplit light beam transmitted by optical beam splitter 35 transmitsimages 51 as images 54 to spectral imaging path 22 received by spectralimage camera 40. The reflected split light beam reflected by opticalbeam splitter 35 reflects images 51 as images 52 to spatial imaging path24 received by spatial image camera 30. Spatial imaging path 24 isproduced by optical and other devices, as described in further detailbelow. Spectral imaging path 22 is produced by optical and otherdevices, as described in further detail below. In some exampleconfigurations of spatial-spectra imaging apparatus 20, respectivedevices for spatial imaging path 22 and spectral imaging path 24 may beswapped such that spatial imaging path 24 receives transmitted images 54from beam splitter 35 and spectral imaging path 24 receives reflectedimages 52 from beam splitter 35.

Spatial imaging path 24 includes a relay optical lens 26, coupled tobeam splitter 35 via an optional spacer, to operate on images 52. Therelay optical lens 26 adjusts the size of the spatial image so that itis compatible with the size of the film or digital mage sensor of thespatial image camera 30. An optional filter compartment 28 may be loadedwith an optical filter to filter one or more wavelengths of images 52.The choice of filter may be application-dependent. For imaging fundus49, for instance, optional filter compartment 28 may be loaded with ared filter to enhance contrast for images 52 of the fundus 49 to berecorded by spatial image camera 30. Spatial image camera 30 mayrepresent a digital or film camera. Spatial image camera 30 mayrepresent a color or monochromatic camera. Spatial image camera 30records images 52 as one or more recorded spatial images. An examplerecorded spatial image is shown in FIG. 2.

Spectral imaging path 22 includes a relay optical lens 34, coupled tobeam splitter 35 via an optional spacer, to operate on images 54. Therelay optical lens 34 adjusts the size of the spectral image so that itis compatible with the size of the film or digital mage sensor of thespectral image camera 40. The relay optical lens 34 may also set theimage focus at the position of the entrance slit 36 of the spectrograph36. A spectrograph mount 33 is configured to attach imaging spectrograph36 to relay optical lens 34. A camera mount 38 is configured to attachspectral image camera 40 to imaging spectrograph 36. Spectral imagecamera 40 may represent a digital or film camera. Spectral image camera40 may represents a monochromatic camera.

Spectral imaging path 22 may or may not include a filter compartment,i.e., images may pass unfiltered to spectrograph 36 fromophthalmological lens 14. As a result, in some configurations, spatialimage camera 30 may receive filtered images of images 50, while spectralimage camera 40 may receive unfiltered images of images 50.

An entrance slit of imaging spectrograph 36 receives images 54 from beamsplitter 35. The entrance slit may be located in the body of the imagingspectrograph 36 and defines an area of images 54 that passes to and isdispersed by the imaging spectrograph 36. The entrance slit may have awidth between 1-100 μm in some examples. The area of images 54 thatpasses to the imaging spectrograph may substantially conform to the lineshape of the entrance slit.

Imaging spectrograph 36 separates (or “disperses”) wavelengths includedin the area of images 54 into continuous two-dimensional spectra thatforms across the lengthwise dimension of the entrance slit, havingwavelength axes substantially transverse to the lengthwise-dimension ofthe entrance slit of the imaging spectrograph 36. In other words, theentrance slit disperses wavelengths to form spectra whose wavelengthaxes are parallel to the transverse direction of the entrance slit. Fora digital camera, this same direction of the spectra may be orientedwith columns (or rows) of pixels on a two-dimensional image sensor ofthe digital camera. The entrance slit creates spectra continuously atevery point along its length, which may be oriented parallel to rows (orcolumns) of pixels on a two-dimensional image sensor of a digitalcamera. The spatial-spectral image created by this process may berecorded as a single image frame.

The continuous spectra for the area of images 54 form a spectral image57 output to spectral image camera 40, which records spectral images 57as one or more recorded spectral images and stores the recorded spectralimages to a storage medium, such as a hard drive. An example recordedspectral image is shown in FIG. 3. Because the digital camera imagesensor has discrete detection elements, a recorded spectral image 57represents multiple spectra having wavelength axes parallel to thetraverse direction of the entrance slit. Post-processing of a recordedspectral image 57 may be used to combine two or more spectra of therecorded spectral image 57 for display or analysis.

In some examples, beam splitter 35 is configured to reflectapproximately 30% of the light beam from output port 17 along imagingpath 24 and to transmit approximately 70% of the light beam alongimaging path 22. A higher proportion of the light beam received atspectral image camera 40 versus spatial image camera 30 in this way maycompensate for the spectral dilution of wavelengths along pixels ofspectral images 57 recorded by spectral image camera versus the spatialimages 52 recorded by spatial image camera 30.

Imaging system 10 includes a trigger device 60 (“trigger 60”)communicatively coupled, via respective signal links 62 and 64, tospatial image camera 30 and spectral image camera 40. Signal links 62and 64 may represent wired or wireless links for transmitting signalsthat, when received by cameras 30 and 40, cause the cameras to take aphotograph. Trigger 60 may represent any electronic apparatus configuredto source triggers, such as packets, electrical signals, opticalsignals, or other types of signals to cause camera 30 and 40 to takephotographs. Common trigger 60 may be manually or automaticallyinitiated. For example, a user (such as a clinician or researcher) maymanually press a button of trigger 60 that initiates respective signalsto cameras 30 and 40. As another example, a periodic timer of trigger 60may initiate signals to cameras 30 and 40. For fundus or otherophthalmological applications, a user of imaging system 10 may direct agaze of the subject using an articulating light system or with verbalinstructions and initiate trigger 60 when the gaze of the subject is ina desired direction.

In some examples, including the illustrated example of FIG. 1, trigger60 is also communicatively coupled, via signal link 65, to retinalviewing device 12. The common trigger 60 may further signal retinalviewing device 12 to, e.g., illuminate the subject (e.g., fundus 49) bygenerating a flash. The signal sent via signal link 65 may besynchronous with signals sent via signal links 62, 64 such that thecameras 30 and 40 take photographs of subjects illuminated by theretinal viewing device 12.

Spectral image camera 40 and spatial image camera 30 are configured torecord images (e.g., take photographs) in response to receiving signalsfrom trigger 60. When triggered by common trigger 60, spectral imagecamera 40 and spatial image camera 30 synchronously record a spectralimage from spectral images 57 and spatial image from images 52,respectively. Spectral image camera 40 and spatial image camera 30 mayrecord association data in association with respective recorded imagesto enable subsequent association of the recorded images as representinga spatial image and spectral image recorded at the same time (i.e.,synchronously). Association data may represent an image number stored byeach camera 30, 40 for images (e.g., an integer indicating the 1st, 2nd,etc. photograph taken for a session, and in some cases indicating in afile name for a recorded image), a timestamp, or other data indicatingthat a given pair of recorded spectral and spatial images correlate intime.

In this way, the imaging system 10 synchronously records a spatial imageand a spectral image of a portion of the spatial image. As noted above,the entrance slit of the imaging spectrograph defines an area of theimages 54 that passes to the imaging spectrograph 36, by which the lightfrom the area is dispersed into a continuous set of spectra, and isrecorded by the spectral image camera 40. Because the first split beamcarrying images 54 and the second split beam carrying images 52 aresplit from a common optical beam carrying images 51, the entrance slitof the imaging spectrograph 36 defines the area of a given image that isseparated into spectra and correlates to a corresponding area of thespatial image. The imaging system 10 may consequently enable thesynchronous recording of a spectral image of the optical spectra ofpoints in a defined area of an image together with a recording of thespatial image for the spectral image that includes the defined area. Insome examples, the imaging system 10 produces spectra with evenly spacewavelengths, up to several hundred wavelengths over the visible and nearinfrared range. Because the optical spectra of points in the definedarea of the image map to the corresponding points in the spatial image,the imaging system 10 may enable the assignment of optical spectradirectly to physical features contained in a conventional image, byvirtue of the one-to-one mapping between a spectra and a location in theimages. In other words, the imaging system 10 and techniques describedhere may allow users to produce a substantially exact and documentedassignment between recordings of optical spectra and the specificphysical or structural features of the measured object.

The imaging system 10 may in this way provide advantages over imagingsystems in which optical spectra from a single line on an object areobtained by exposing the camera to light reflected from the object, andin which the location where spectra originate on the object areapproximately determined based on a separate, subsequent (i.e.,non-synchronous) picture of the recorded surface. For example, theimaging system 10 may be particularly applicable for applications inwhich the object that is the image source is not precisely controlled bythe user, e.g., has independent motion as in the case of human or otherliving subjects, or in which the object is sensitive to light. Forinstance, the imaging system 10 may be particularly applicable wheremotion-controlled moving platform hyperspectral imaging is not feasible.The imaging system 10 may enable the desired co-assignment of highresolution spectra and object features when it is not necessary toobtain the optical spectrum of every point on a grid, but fulldocumentation of object features around the measured line arenonetheless desirable.

FIG. 2 is a recorded spatial image 100 of the optic disc and retinalsurround of a human subject's eye. Line 102 depicts an area of thespatial image 100 that is input to an imaging spectrograph to produce aspectral image synchronously recorded by imaging system 10, as describedin this disclosure. Line 102 may correspond in location to an entranceslit of imaging spectrograph 36 of imaging system 102. In some examples,line 102 may span the entire width of spatial image 100. In someexamples, line 102 may have a width of one or more pixels.

FIG. 3 is a recorded spectral image 150 which depicts the opticalspectrum of each point along line 102 crossing the spatial image 100 ofFIG. 2, according to techniques described herein. The spectral image 150depicts the optical wavelengths of the spectrum along the vertical imagedimension, and a one-dimensional image of the object along thehorizontal dimension, which corresponds to the center horizon of thespatial image 100. The position of the center horizon in the spatialimage 100 is fixed and depicted in FIG. 2 by line 102. As a furtherillustration of the relationship between images, the brightly reflectingoptic disc in the spatial image 100 is associated with a bright band,the spectrum of the disc, in the spectral image 150. Also, blood vesselsin the spatial image 100 correspond to the location of dark verticalbands in the spectral image 150. Each column of pixels of spectral image150 may represent a spectrum for the width of a single pixel on line 102of spatial image 100. Reflected light spectral plots may be obtainedusing an image analysis program to measure the light along a verticalline in the spectral image, which is later the object of variousspecific spectral analyses.

Spatial image 100 and spectral image 150 may be recorded using imagingsystem 10 according to techniques described in this disclosure.

In order to identify a location of spatial image 100 that corresponds toa spectra of spectral image 150 so as to directly map spectra tocoordinates of the spatial image 100 and physical features, the locationof line 102 for instances of spatial image 100 recorded by the imagingsystem 10 may be determined. In some examples, a user may create atarget having a discrete contrast agent. By precisely controlling themotion of the target and moving the target until the recorded spectralimage indicates that recorded spectra are for the contrast agent, a userof imaging system 10 may determine from synchronously recorded spatialimage the location of line 102.

FIG. 4 is a plot of the computed absorption spectrum 200 of capillaryblood from the optic disc in the visible light spectrum, in accordancewith techniques of this disclosure. The imaging system 10 described inthis disclosure may be used to synchronously record spatial and spectralimages for a subject. The spatial and spectral images may be usable todetect ophthalmological conditions, retinal diseases, or Alzheimer'sdisease. Example description for using images to detect Alzheimer'sdisease is found in U.S. Patent Publication 2014/0348750, published Nov.27, 2014, which is incorporated by reference herein in its entirety. Thecomputed absorption spectrum is the spectrum produced by capillary bloodin the disc tissue, representing oxyhemoglobin. The absorption spectrumis obtained using vertical line profiles from the retinal image and ablank image of a neutral reflecting surface, which together are used tocalculate the light absorption. The same or similar image analysisprocedures may be used to detect optical signals that representearly-stage Alzheimer's disease. The effects of light scattering fromthe blood and other small molecules in the retina are also present inthis spectrum.

FIG. 5 is a diagram illustrating a conceptual view of select parts of ahuman fundus. Diagram 300 illustrates an optic disc 302, a nerve fiberlayer and multiple blood vessels 304, an upper retinal area (“upperretina”) 306, a lower retinal area (“lower retina”) 308, and perifovea.A user of imaging system 10 may focus ophthalmological lens 14 toconfigure imaging system 10 to synchronously capture one or more spatialand spectral images 50 for parts of a subject fundus 49, including anyof the parts illustrated in diagram 300.

FIG. 6 includes spatial images recorded by operation of an imagingsystem 10, according to techniques described herein. Spatial image 400is an image of an optic disc of an example of a subject fundus 49.Spatial image 410 is an image of a nerve fiber layer of an example of asubject fundus 49. Spatial image 420 is an image of a macula of anexample of a subject fundus 49. Spatial image 430 is an image of aretina of an example of a subject fundus 49.

FIGS. 7A-7D each depicts a correlated, recorded pair of spatial andspectral images of a part of a human fundus, recorded by operation of animaging system 10 according to techniques described in this disclosure.For each pair of spatial-spectral images, the spectral image depicts theoptical wavelengths of the spectrum along the vertical image dimension,and a one-dimensional image of the object along the horizontaldimension, which corresponds to the center horizon of the spatial image.FIG. 7A depicts a correlated spatial image 480A and spectral image 480B,of an optic disc. FIG. 7B depicts a correlated spatial image 482A andspectral image 482B, of a nerve fiber layer. FIG. 7C depicts acorrelated spatial image 484A and spectral image 484B, of a retina. FIG.7D depicts a correlated spatial image 486A and spectral image 486B, of amacula.

FIGS. 8-9 include spatial images recorded by operation of an imagingsystem 10, according to techniques described herein. Spatial image 500is an image of a retina of a human who has not been diagnosed withAlzheimer's disease. Spatial image 510 is an image of a retina of ahuman who has been diagnosed with Alzheimer's disease.

FIGS. 10A-10D each depict a plot of average absorption spectra ofcapillary blood from a part of human fundi, in the visible lightspectrum, computed according to techniques described herein. The imagingsystem 10 described in this disclosure may be used to synchronouslyrecord spatial and spectral images for a subject. The computedabsorption spectrum is the spectrum produced by capillary blood in thedisc tissue, representing oxyhemoglobin. The absorption spectrum isobtained using vertical line profiles from the retinal image and a blankimage of a neutral reflecting surface, which together are used tocalculate the light absorption.

Each of plots 600A-600D includes an average absorption spectrum for aset of control subjects (11 subjects in the example data set used tocompute the spectra) and an average absorption spectrum for a differentset of Alzheimer's subjects each having an Alzheimer's diagnosis (5subjects in the example data set used to compute the spectra). Eachsubject presents a different absorption spectrum, with the averageabsorption spectrum for a set computed as the average of the values ofthe respective absorption spectra per wavelength data point.

Plot 600A depicts an average absorption spectrum 602A for the set ofAlzheimer's subjects and an average absorption spectrum 604A for the setof control subjects, spectra 602A, 604A computed using spectra fromspectral images of optic discs, captured using an example of imagingsystem 10.

Plot 600B depicts an average absorption spectrum 602B for the set ofAlzheimer's subjects and an average absorption spectrum 604B for the setof control subjects, spectra 602B, 604B computed using spectra fromspectral images of macula, captured using an example of imaging system10.

Plot 600C depicts an average absorption spectrum 602C for the set ofAlzheimer's subjects and an average absorption spectrum 604C for the setof control subjects, spectra 602C, 604C computed using spectra fromspectral images of retina nerve fiber layers (RNFL), captured using anexample of imaging system 10.

Plot 600D depicts an average absorption spectrum 602D for the set ofAlzheimer's subjects and an average absorption spectrum 604D for the setof control subjects, spectra 602D, 604D computed using spectra fromspectral images of retinas, captured using an example of imaging system10.

FIGS. 11A-11D each depict a plot of average absorption spectra ofcapillary blood from a part of human fundi, in the visible lightspectrum, computed according to techniques described herein. The imagingsystem 10 described in this disclosure may be used to synchronouslyrecord spatial and spectral images for a subject. The computedabsorption spectrum is the spectrum produced by capillary blood in thedisc tissue, representing oxyhemoglobin. The absorption spectrum isobtained using vertical line profiles from the retinal image and a blankimage of a neutral reflecting surface, which together are used tocalculate the light absorption.

Each of plots 700A-700D includes an average absorption spectrum for theset of control subjects and an average absorption spectrum for the setof Alzheimer's subjects from the data set for plots 600. Plots 700A-700Dalso include respective average absorption spectra 706A-706D for anadditional data set of subjects presenting early stage Alzheimer'sdisease. Each subject presents a different absorption spectrum, with theaverage absorption spectrum for a set computed as the average of thevalues of the respective absorption spectra per wavelength data point.

The techniques described herein may be implemented in hardware,software, firmware, or any combination thereof. Various featuresdescribed as modules, units or components may be implemented together inan integrated logic device or separately as discrete but interoperablelogic devices or other hardware devices. In some cases, various featuresof electronic circuitry may be implemented as one or more integratedcircuit devices, such as an integrated circuit chip or chipset.

If implemented in hardware, this disclosure may be directed to anapparatus such as a processor or an integrated circuit device, such asan integrated circuit chip or chipset. Alternatively or additionally, ifimplemented in software or firmware, the techniques may be realized atleast in part by a computer-readable data storage medium comprisinginstructions that, when executed, cause a processor to perform one ormore of the methods described above. For example, the computer-readabledata storage medium may store such instructions for execution by aprocessor.

A computer-readable medium may form part of a computer program product,which may include packaging materials. A computer-readable medium maycomprise a computer data storage medium such as random access memory(RAM), read-only memory (ROM), non-volatile random access memory(NVRAM), electrically erasable programmable read-only memory (EEPROM),Flash memory, magnetic or optical data storage media, and the like. Insome examples, an article of manufacture may comprise one or morecomputer-readable storage media.

In some examples, the computer-readable storage media may comprisenon-transitory media. The term “non-transitory” may indicate that thestorage medium is not embodied in a carrier wave or a propagated signal.In certain examples, a non-transitory storage medium may store data thatcan, over time, change (e.g., in RAM or cache).

The code or instructions may be software and/or firmware executed byprocessing circuitry including one or more processors, such as one ormore digital signal processors (DSPs), general purpose microprocessors,application-specific integrated circuits (ASICs), field-programmablegate arrays (FPGAs), or other equivalent integrated or discrete logiccircuitry. Accordingly, the term “processor,” as used herein may referto any of the foregoing structure or any other structure suitable forimplementation of the techniques described herein. In addition, in someaspects, functionality described in this disclosure may be providedwithin software modules or hardware modules.

In addition to or as an alternative to the above, the following examplesare described. The features described in any of the following examplesmay be utilized with any of the other examples described herein.

Example 1. A spatial-spectral imaging apparatus comprising: a beamsplitter configured to receive a light beam carrying an image of anobject and to split the light beam into a first split light beam and asecond split light beam; an imaging spectrograph configured to receivethe first split light beam and separate a range of wavelengths of thefirst split light beam to form a spectral image comprising a pluralityof spectra; a spatial image camera configured to receive the secondsplit light beam; and a spectral image camera configure to receive thespectral image from the imaging spectrograph, wherein the spectral imagecamera and the spatial image camera are configured to synchronouslyrecord, respectively, the spectral image and a spatial image carried bythe second split light beam.

Example 2. The spatial-spectral imaging apparatus of claim 1, whereinthe beam split is configured to split approximately 70% of the lightbeam into the first split light beam and approximately 30% of the lightbeam into the second split light beam.

Example 3. The spatial-spectral imaging apparatus of claim 1, furthercomprising: a trigger device configured to send, in response to a commontrigger, the spatial image camera and the spectral image camerarespective signals, wherein the spatial image camera and the spectralimage camera are configured to, in response to receiving the respectivesignals, synchronously record the spatial image carried by the secondsplit light beam and the spectra image, respectively.

Example 4. The spatial-spectral imaging apparatus of claim 1, whereinthe first split light beam carries a first image corresponding to theimage and the second split light beam carries a second imagecorresponding to the image, wherein the imaging spectrograph comprisesan entrance slit that defines an area of the first image input to theimaging spectrograph and separated into the range of wavelengths to formthe spectral image.

Example 5. The spatial-spectral imaging apparatus of claim 4, whereinthe area of the first image correlates to a corresponding area of thesecond image.

Example 6. The spatial-spectral imaging apparatus of claim 4, whereineach spectra of the plurality of spectrum maps to a point in the secondimage.

Example 7. The spatial-spectral imaging apparatus of claim 4, whereinthe first image comprises: the range of wavelengths for each spectrum ofthe plurality of spectra in a first dimension; a one-dimensional imageof the object in a second dimension, wherein a horizon of the secondimage corresponds to the one-dimensional image of the object in thesecond dimension.

Example 8. The spatial-spectral imaging apparatus of claim 1, whereinthe range of wavelengths is evenly spaced.

Example 9. The spatial-spectral imaging apparatus of claim 1, whereinthe range of wavelengths comprises >30 wavelengths.

Example 10. The spatial-spectral imaging apparatus of claim 1, whereinthe range of wavelengths comprises >100 wavelengths.

Example 11. The spatial-spectral imaging apparatus of claim 1, whereinthe spatial image camera is configured to generate a recorded spatialimage of the spatial image, and wherein the spectral image camera isconfigured to generate a recorded spectral image of the spectral image.

Example 12. The spatial-spectral imaging apparatus of claim 1, furthercomprising: an adapter to attach the spatial-spectral imaging apparatusto a retinal viewing device configured to output the light beam carryingthe image of the object.

Example 13. The spatial-spectral imaging apparatus of claim 1, furthercomprising: a filter compartment for an optical filter, the filtercompartment located on an imaging path of the second split light beam.

Example 14. The spatial-spectral imaging apparatus of claim 1, whereinthe spectral image camera is configured to store first association datafor the spectral image, and wherein the spatial image camera isconfigured to store second association data for the spatial image, thefirst association data and the second association data usable fordetermining the spectral image and the spatial image were synchronouslyrecorded.

Example 15. An imaging system comprising: a retinal viewing deviceconfigured to output a light beam carrying an image of an object; andthe spatial-spectral imaging apparatus of any of claims 1-14.

Example 16. The spatial-spectral imaging apparatus of claim 15, whereinthe retinal viewing device comprises a fundus camera.

Example 17. A method comprising: triggering a spatial-spectral imagingapparatus of any of claims 1-14 to trigger the spectral image camera andthe spatial image camera to synchronously record images.

Example 18. The method of claim 17, wherein the images are of an objecthaving inherent motion not directly under the control of the user of thespatial-spectral imaging apparatus.

Example 19. The method of claim 17, further comprising: associating arecorded spatial image recorded by the spatial image camera and arecorded spectral image synchronously recorded by the spectral imagecamera.

Example 20. The method of claim 19, further comprising: based on theassociation of the recorded spatial image and the recorded spectralimage, mapping a spectra of the plurality of spectrum of the recordedspectral image to a point in the recorded spatial image.

Example 21. A method comprising detecting a retinal disease or otherdisease that presents symptoms through a retina, using aspatial-spectral imaging apparatus of any of claims 1-14.

Example 22. A method comprising detecting one of wound healing,Alzheimer's disease, and aging effects in skin, using a spatial-spectralimaging apparatus of any of claims 1-14.

Example 23. A method comprising performing any of the applications ofthis disclosure, using a spatial-spectral imaging apparatus of any ofclaims 1-14.

Moreover, any of the specific features set forth in any of the examplesdescribed above may be combined into beneficial examples of thedescribed techniques. That is, any of the specific features aregenerally applicable to all examples of the invention. Various examplesof the invention have been described.

What is claimed is:
 1. A method comprising: forming, with an imagingapparatus, a spectral image and a spatial image; synchronouslygenerating, with the imaging apparatus, a recorded spectral image of thespectral image and a recorded spatial image of the spatial image,wherein the recorded spectral image comprises multiple optical spectrain a defined area that map to corresponding points in the recordedspatial image to enable the assignment of individual optical spectra ofthe recorded spectral image to physical features in the recorded spatialimage.
 2. The method of claim 1, wherein wavelengths in each of themultiple optical spectra are evenly spaced.
 3. The method of claim 1,wherein the spectral image is a hyperspectral image.
 4. The method ofclaim 1, wherein the spectral image and the spatial image are formedfrom an image of an object.
 5. The method of claim 4, wherein the objectis a human fundus of a live human subject.
 6. The method of claim 4,further comprising: processing the recorded spectral image to compute anabsorption spectrum for a patient; and detecting, based on theabsorption spectrum for the patient, an indication of Alzheimer'sdisease in the patient.
 7. The method of claim 6, further comprising:identifying, based on the recorded spatial image, locations of a featurewithin the object; and mapping the locations to one or more spectra ofthe optical spectra of the recorded spectral image, wherein processingthe recorded spectral image to compute an absorption spectrum for apatient comprise computing the absorption spectrum of the one or morespectra of the optical spectra of the recorded spectral image.
 8. Themethod of claim 7, wherein the feature comprises one of an optic disc, aretinal area, or a perifovea.
 9. The method of claim 1, wherein thespectral image and the spatial image are formed from a common opticalbeam.
 10. The method of claim 9, wherein the common optical bean carriesan image of an object, and wherein the defined area is a defined area ofthe image of the object.
 11. The method of claim 1, wherein the spatialimage and the spectral image are of an object having inherent motion.12. The method of claim 1, further comprising: associating the recordedspatial image and the recorded spectral image; and based on theassociation of the recorded spatial image and the recorded spectralimage, mapping a spectrum of the plurality of spectra of the recordedspectral image to a point in the recorded spatial image.
 13. The methodof claim 1, wherein the imaging apparatus comprises: a first imagesensor for generating the recorded spectral image of the spectral image;and a second image sensor for generating, synchronously with thegenerating of the recorded spectral image, the recorded spatial image ofthe spatial image.
 14. A method comprising: forming, with an imagingapparatus, a spectral image and a spatial image; synchronouslygenerating, with the imaging apparatus, a recorded spectral image of thespectral image and a recorded spatial image of the spatial image,wherein the recorded spectral image comprises multiple optical spectraalong a first image dimension and a one-dimensional image along a secondimage dimension that corresponds to a center horizon of the recordedspatial image to enable the assignment of individual optical spectra ofthe recorded spectral image to physical features in the recorded spatialimage.
 15. The method of claim 14, wherein wavelengths in each of themultiple optical spectra are evenly spaced.
 16. The method of claim 14,wherein the spectral image is a hyperspectral image.
 17. The method ofclaim 14, wherein the spectral image and the spatial image are formedfrom a common optical beam.
 18. The method of claim 14, wherein thespatial image and the spectral image are of an object having inherentmotion.
 19. The method of claim 14, based on an association of therecorded spatial image and the recorded spectral image, mapping aspectrum of the plurality of spectra of the recorded spectral image to apoint in the recorded spatial image.
 20. The method of claim 14, whereinthe imaging apparatus comprises: a first image sensor for generating therecorded spectral image of the spectral image; and a second image sensorfor generating, synchronously with the generating of the recordedspectral image, the recorded spatial image of the spatial image.
 21. Aretinal imaging apparatus comprising: a first image sensor; and a secondimage sensor, wherein the first image sensor and the second image sensorare configured to receive light carrying an image of an object andsynchronously record the image of the object to generate, respectively,a recorded spectral image of the image of the object and a recordedspatial image of the image of the object, the recorded spectral imagecomprising multiple optical spectra in a defined area of the image ofthe object that map to corresponding points in the recorded spatialimage to enable the assignment of individual optical spectra of therecorded spectral image to physical features in the recorded spatialimage.